> -----Original Message----- > From: Byungchul Park [mailto:byungchul.p...@lge.com] > Sent: Thursday, February 23, 2017 12:11 PM > To: pet...@infradead.org; mi...@kernel.org > Cc: linux-kernel@vger.kernel.org; juri.le...@gmail.com; > rost...@goodmis.org; kernel-t...@lge.com > Subject: [PATCH v2 2/2] sched/deadline: Change the way to replenish > runtime for sleep tasks > > Let's consider the following example. > > timeline : o...................o.........o.......o..o > ^ ^ ^ ^ ^ > | | | | | > start | | | | > original runtime | | | > sleep with (-)runtime | | > original deadline | > wake up > > When this task is woken up, a negative runtime should be considered, > which means that the task should get penalized when assigning runtime, > becasue it already spent more than expected. > > Current code handles this by replenishing a runtime in hrtimer callback > for deadline. But this approach has room for improvement in two ways: > > 1. No need to keep the hrtimer for a sleep task because it can be > handled when waking it up. > > 2. It will be replenished twice unnecessarily if the task sleeps for > long time so that the deadline, assigned in the hrtimer callback, > also passed. In other words, one happens in the callback and the > other happens in update_dl_entiry() when waking it up. > > So try to cancel the hrtimer for a sleep task and make all these things > handled when waking it up. > > Signed-off-by: Byungchul Park <byungchul.p...@lge.com> > --- > kernel/sched/deadline.c | 9 +++++++-- > 1 file changed, 7 insertions(+), 2 deletions(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 69e3fbb..b59ee7b 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -507,8 +507,10 @@ static void update_dl_entity(struct sched_dl_entity > *dl_se, > struct dl_rq *dl_rq = dl_rq_of_se(dl_se); > struct rq *rq = rq_of_dl_rq(dl_rq); > > - if (dl_time_before(dl_se->deadline, rq_clock(rq)) || > - dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) { > + if (dl_time_before(dl_se->deadline, rq_clock(rq))) > + __replenish_dl_entity(dl_se, pi_se); > + > + if (dl_entity_overflow(dl_se, pi_se, rq_clock(rq))) { > dl_se->deadline = rq_clock(rq) + pi_se->dl_deadline; > dl_se->runtime = pi_se->dl_runtime; > } > @@ -981,6 +983,9 @@ static void dequeue_task_dl(struct rq *rq, struct > task_struct *p, int flags) > { > update_curr_dl(rq); > __dequeue_task_dl(rq, p, flags); > + > + if (flags & DEQUEUE_SLEEP) > + hrtimer_try_to_cancel(&p->dl.dl_timer);
Sorry. I found I might have made a mistake. I might have to re-start the timer when waking it up if necessary. Let me think more. > } > > /* > -- > 1.9.1
